@gianarb unfortunately often the answer is „you just have to know, somehow“.
There are countless moving parts in the Nix ecosystem which are not (well) documented. Experienced users usually don’t notice this friction any more because they learned to help themselves. Clearly this is inefficient because it usually takes many months to get there.
If you have the time and energy to help by contributing what you have learned into official documentation, we will help you get things merged. Please check How to contribute to documentation for details. The contribution process (meta-documentation) also needs feedback by beginners, because there also you usually have to „just know“ may things, and we want to make them explicit.